This invention relates to the field of wireless communication systems. More specifically, the present invention relates to a power management system for mobile stations.
The use of wireless communication systems is growing every day with users now numbering well into the millions. Mobile stations, such as handheld telephones, are becoming more portable and easier to use all the time, and mobile station users now rely daily on the availability of wireless systems to accommodate their communication needs. However, the single greatest inconvenience associated with routine use of a mobile station is the constant need to recharge and replace worn down batteries. Even users who make and receive very few telephone calls and operate their mobile stations mostly in the standby mode (awaiting calls) experience the annoying and frequent problem of the mobile station running out of battery power thus becoming dead and useless until the worn battery is replaced with a charged battery. Users demand mobile stations having the longest possible battery life.
A large portion of battery power consumed in standby mode is attributable to call detection processing. For example, in GSM-based wireless communication networks, about once every second a mobile station receives and decodes a full paging message comprising four groups of digital data transmitted at certain time intervals to detect any calls. Only rarely does the detection attempt result in discovery of a telephone call for the mobile station. A great deal of battery power is consumed in this call detection process.
Also, while in standby mode, a mobile station periodically receives and processes transmitted broadcast control data including information about communication parameters (channels, frequencies, communication options, etc.). Existing mobile stations receive and process broadcast control data frequently and without fail, for example every 30 seconds, regardless of whether the information contains anything useful to the mobile station. Again, battery power is consumed by this processing even where the mobile station obtains no new information.
Battery power is even consumed when the mobile station is performing no receiving and processing whatsoever. This is because existing mobile stations use a very high precision master clock that runs continuously. Such master clocks are extremely precise and permit the mobile stations to engage in precisely timed communication as required by many wireless communications standards, and particularly by those such as GSM which depend on time division multiple access wherein mobile stations are allocated very short time periods within which to communicate. The high precision of master clocks comes at a price, however, as such master clocks consume battery power at a much higher rate than clocks having lower precision.
Improvements in battery technology, while helpful, have done little to avoid the seemingly ever-present need to recharge and replace mobile station batteries. What is needed is a system to conserve battery power by minimizing mobile system processing, particularly in standby mode.
The present invention is directed to reducing power consumed by a mobile station operating in standby mode. The present information reduces the quantity of data that the mobile station receives and processes to detect pending telephone calls or paging messages. The reduced processing consumes, less power and advantageously increases the standby mode lifetime of a mobile station battery. Moreover, the present invention reduces the frequency with which the mobile station receives and processes broadcast control information while preserving the ability of the mobile station to detect and process any updated information in a broadcast control channel. Processing fewer broadcast control channels also has the advantage of increasing the lifetime of a mobile station battery. Further, the invention reduces the power consumed by the mobile station when completely idle (i.e., when the mobile station is not receiving, transmitting, or processing any data), still further increasing the lifetime of a mobile station battery.
In one embodiment of the present invention, a mobile station comprises: (1) a software instruction processing unit; (2) a software instruction storage comprising a computer-readable medium, the software instruction storage accessible to the software instruction processing unit; (3) a short page channel receiving module stored in the software instruction storage, the short page channel receiving module including receiving instructions executed by the software instruction processing unit, the receiving instructions causing the mobile station to scan broadcast information in a wireless communication network for a short page channel and to receive a single time slot of the short page channel containing one group of call alert data; and (4) a short page processing module stored in the software instruction storage, including processing instructions executed by the software instruction processing unit, the processing instructions causing the mobile station to process the one group of call alert data and to determine from the group of call alert data whether a pending telephone call or paging message may have been directed to the mobile station. A preferred aspect of the mobile station further comprises: (1) an idle state wherein the mobile station does not scan for a short page channel or receive or process call alert information, the mobile station entering the idle state during a time period between broadcasts of the short page channel; and (2) a battery providing power to the mobile station, the mobile station consuming the power at a first rate during the scanning for the short page channel and during receiving or processing the call alert information, the mobile station consuming the power at a second rate in the idle state, the second rate being less than the first rate. A further preferred aspect of the mobile station further comprises: (1) a master clock; and (2) a low precision clock, the low precision clock being sufficiently precise to time the receipt of a single short page channel time slot, the low precision clock less precise than the master clock, the low precision clock consuming less power during a time interval than the master clock, the low precision clock timing the idle state, the master clock shut down during the idle state.
In another embodiment, a mobile station comprises: (1) a call alert module structured to extract an alert message from transmitted call alert data, the call alert module responding to call alert data received from a call alert channel of a wireless communication system by alerting the mobile station of a pending telephone call or paging message which may be directed to the mobile station; and (2) a paging module structured to extract a paging message from transmitted paging data, the paging module responding to paging data received from a paging channel of the wireless communication system by determining whether the telephone call or paging message is directed to the mobile station, the alert data requiring less processing than the paging data. A preferred aspect of the mobile station further comprises a call establishment module which initiates the establishment of a communication link to a communication device responsible for initiating the telephone call or paging message, the call establishment module invoked upon the determining that the telephone call or paging message is directed to the mobile station.
In a further embodiment of the present invention, a cellular system comprises: (1) a base station; (2) a cell; (3) a receiver in the cell; (4) an alert channel in which the base station transmits within the cell alert information to alert the receiver of a pending telephone call or paging message; and (5) a paging channel in which the base station transmits within the cell paging information to notify a receiver that the receiver is the intended recipient of said telephone call or paging message, the paging information requiring less processing by the receiver than the alert information. In a preferred aspect, the cellular system further comprises receiver identity information within the alert information, the receiver identity information not uniquely identifying the receiver.
In still another embodiment of the present invention, a mobile station, with reduced standby processing requirements, comprises: (1) a data storage area; (2) a paging group value stored in the data storage area, the paging group value specifying first paging channels, the paging group value assigned to the mobile station by a mobile switching center; and (3) a paging channel skipping value stored in the data storage area, the paging channel skipping value specifying a subset of the first paging channels, the subset identifying paging channels transmitted less frequently than said first paging channels, the mobile station receiving and processing the subset of the first paging channels.
In a still further embodiment of the present invention, a short page channel time slot is stored in a computer-readable medium. The short page channel comprises: (1) mobile station identity information from which a mobile station receiving the short page channel time slot as part of a broadcast TDMA frame determines that a pending telephone call or paging message may have been directed to the mobile station; and (2) error detection information from which a mobile station receiving the error detection information along with the mobile station identity information in the short page channel time slot determines whether data received in the short page channel time slot contains errors.
In another embodiment of the present invention, a mobile switching center comprises: (1) a data storage area, the data storage area containing a mobile station identifier value associated with a mobile station; and (2) a short page channel creation module invoked by the mobile switching center upon detection by the mobile switching center that a telephone call is being directed to the mobile station, the short page channel creation module combining in a single time slot of a TDMA frame the mobile station identifier value and error detection data, the mobile switching center including the single time slot of the TDMA frame within a multiframe for transmission to a base station. In a preferred aspect, the mobile switching center further comprises a bit for updating broadcast control information, the bit combined in the single time slot, the bit having a first value if the content of the most recently transmitted broadcast control channel in a particular cell did not change from the content of an inmmediately preceding broadcast control channel transmitted to the same cell, the bit having a second value if the content of the recently transmitted broadcast control channel is different from the content of the immediately preceding broadcast control channel.
In yet another embodiment of the present invention, a mobile station, with reduced requirements for processing broadcast control data, comprises: (1) a data storage area; (2) a short page channel data buffer in the data storage area including a bit reserved for updating broadcast control information, the bit received by the mobile station from a time slot of a TDMA frame; (3) a software instruction storage in a computer-readable medium; (4) a broadcast control update module stored in the software instruction storage, the broadcast control update module responding to receipt of the bit by comparing the bit to a prior received bit stored in the data storage area and, if the compared bits differ, directing the mobile station to receive and process a next transmitted broadcast control channel to update communication parameters of the mobile station, otherwise if the compared bits are the same, storing the newly received bit in place of the prior received bit.
In another embodiment of the present invention, a mobile station comprises: (1) a master clock; and (2) a low precision clock, the low precision clock consuming less power than the master clock, the low precision clock used to time an idle state wherein the mobile station is not receiving, transmitting, or processing data, the master clock shut down during the idle state.
In still another embodiment of the present invention, a wireless communication system comprises: (1) a mobile switching center, the mobile switching center generating a first single time slot of a short page channel, the first single time slot including a first mobile station identifier value, the mobile switching center transmitting the first single time slot to a base station, the mobile switching center generating a paging channel having four time slots, the four time slots including a second mobile station identifier, the mobile switching center transmitting the four time slots to the base station; (2) a base station which receives the first single time slot and the four time slots, the base station transmitting to a cell the first single time slot in a short page channel and the four time slots in a paging channel; and (3) a mobile station in the cell, the mobile station identified by the first mobile station identifier and by the second mobile station identifier, the mobile station receiving the first single time slot from the short page channel and extracting the first mobile station identifier from the first single time slot to determine that a pending telephone call or paging message may be directed to the mobile station, the mobile station, upon the determination, receiving the four time slots from the paging channel and extracting the second mobile station identifier to conclude that the mobile station is the intended recipient of the telephone call or paging message, the mobile station, upon the conclusion, initiating call establishment procedures to create a communication link between the mobile station and a communication device responsible for initiating the telephone call or paging message. In a preferred aspect, wireless communication system comprises a broadcast control update bit, the update bit included in the first single time slot, the update bit having a first value if the content of a most recently transmitted broadcast control channel in the cell did not change from the content of an immediately preceding broadcast control channel transmitted to the cell, the bit having a second value if the content of the recently transmitted broadcast control channel is different from the content of the immediately preceding broadcast control channel, the mobile station extracting the update bit from the first single time slot and, if the update bit has the second value, then the mobile station receiving and processing a next transmitted broadcast control channel. In another preferred aspect, the wireless communication system comprises: (1) a data storage area in the mobile station; (2) a paging group value stored in the data storage area, the paging group value specifying first paging channels, the paging group value assigned to the mobile station by the mobile switching center; and (3) a paging channel skipping value stored in the data storage area, the paging channel skipping value specifying a subset of the first paging channels, the subset including a number of paging channels fewer than the number of paging channels comprising the first paging channels, the mobile station receiving and processing the subset of the first paging channels. In another preferred aspect, the wireless communication system further comprises: (1) a master clock timing the receipt of the four time slots by the mobile station; (2) a second single time slot, the mobile switching center transmitting the second single time slot to the base station, the base station transmitting to the cell the second single time slot in the short page channel, the mobile station receiving the second single time slot from the short page channel upon determining from the receipt of the first single time slot that a pending telephone call or paging message is not directed to the mobile station; and (3) a low precision clock timing the duration of an idle state wherein the mobile station does not receive, transmit, or process data, the duration of the idle state occurring after the receipt by the mobile station of the first single time slot and before the receipt by the mobile station of the second single time slot, the second single time slot containing sufficient synchronization bits to permit the receipt of the second single time slot, the master clock shut down during the idle state, the low precision clock consuming less power during a time interval than the master clock.
These and other embodiments are described in more detail below.